I use a stethoscope for locating leaks and it works great.  I bought
a 'el cheapo' at the drug store for about $5.00 and replaced the
diaphragm at the end with a 12" piece of 1/8" brass tubing.  You just
run the end of the tubing around the bellows, pneumatics, valves,
tubing, etc.  It will amplify even the tiniest leak and you can zero
right in on the source.

The only trick is with larger leaks.  You will hear the leak even
though the end of the tubing is some distance from the source, but
as you get closer to the leak the sound will get louder, obviously.
It is just a little deceptive.

Caution: _Never_ put the tubing or bell of the stethoscope near a very
large vacuum leak or source.  You can and probable will, rupture your
ear drums.

I also made a bell for the end of the stethoscope, just like the bell
that was on the early styles.  This works good for locating secondary
valves that are leaking in the off position, in players like the
Autopiano.  With the valve chest all assembled and in the piano, I
slide the bell along the face of the pouch board and mark the leakers
with a small piece of masking tape.  The hissing of the leaking valve
will be very subtle, but you can hear it if you listen close.

While running the test roll you can listen to each valve as they
operate and this will leave no doubt in your mind as to which valves
are marginal in their operation.  This sure beats taking it a part
a gazillion times, like I did on the first one I restored.

Tim Mattice